Futuristic water tower—seemingly simple shape, but how tackle a clean topology?
Use simple shapes and pump up the subsurf subdivision

I would suggest to model your object with simple shapes (e.g. cubes for the pillars, an octagon for the top) then add the subsurf modifier and start tweaking the geometry with the modifier activated.




Let the subsurf modifier do the work for you. Use the minimum amount of vertices in order to easily control the shape and let the smoothing flow.